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  <script>
    // 找出数组中 元素为10的下标，有则打印该下标，没有则打印 - 1

    //     * 例如: [88, 20, 10, 100, 50]   
    //       * 例如: [88, 20, 30, 100, 50]  打印 - 1

          //  let arr =[88, 20, 10, 100, 50]
          //     for(let i=0;i<arr.length;i++){
          //          if(arr[i]===10){
          //             console.log(i);
          //          } 
          //     }
    
              let arr = [88, 20, 100, 50]
                for (let i = 0; i < arr.length; i++) {
                  if (arr[i] !== 10) {
                    console.log(-1);
                  }
                }


  </script>
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